Problem: If $a + 6b = -5$ and $5x + 5y + z = 6$, what is $-35x - 24b - 4a - 7z - 35y$ ?
Explanation: $= -4a - 24b - 35x - 35y - 7z$ $= (-4) \cdot (a + 6b) + (-7) \cdot (5x + 5y + z)$ $= (-4) \cdot (-5) + (-7) \cdot (6)$ $= 20 - 42$ $= -22$